Known image forming apparatuses, such as color printers, operate by forming toner images of colors on a plurality of image bearing members. The images are then transferred (i.e., primary transfer) onto another image bearing member so that a color toner image is formed. The color toner image is subsequently transferred (i.e., secondary transfer) onto a sheet. Such an image forming apparatus, generally, includes a cleaning device that collects or removes residual toner on the image bearing member after the transfer onto a sheet (secondary transfer).
An illustrative cleaning device includes a fur brush (an upstream fur brush) provided at a downstream position, with respect to a secondary transfer position, on a path along which the image bearing member moves, another fur brush (a downstream fur brush) provided at a more downstream position than the upstream fur brush, and a bias roller (a cleaning assist member) provided in contact with the image bearing member between the secondary transfer position and the upstream fur brush.
The bias roller is positively biased in an effort the charge of the residual toner on the image bearing member is both charged positively and uniformly. The positively charged residual toner is then removed by the upstream fur brush that is negatively biased. Residual toner failed to be removed by the upstream fur brush is removed by the downstream fur brush that is positively biased. In this manner, residual toner is removed from the image bearing member, whereby the image bearing member is cleaned.
In the foregoing cleaning device, toner adhered to the upstream and downstream fur brushes is rubbed off by cleaning members. However, the bias roller (cleaning assist member) is not cleaned. Therefore, if residual toner adheres to the bias roller, the bias roller is contaminated. Further, if the contamination on the bias roller adheres back to the image bearing member, image failure may occur on the sheet. Moreover, if such contamination scatters to the outside of the cleaning device, the internal components of the image forming apparatus may be contaminated. Particularly, when a sheet conveyance path is provided below the cleaning device, such contamination may adhere to a sheet that is being conveyed, leading to image failure.